1. Field
One or more embodiments herein relate to a nonvolatile memory device.
2. Description of the Related Art
Semiconductor memory devices are storage devices implemented using a semiconductor material such as silicon (Si), germanium (Ge), gallium arsenide (GaAs), and indium phosphide (InP).
Memory devices of this type may be classified as volatile or nonvolatile. In a volatile memory device, data is lost when power is turned off. Examples of this kind of device include an SRAM (Static RAM), a DRAM (Dynamic RAM), and a SDRAM (Synchronous DRAM). In a nonvolatile memory device, data is retained when power is turned off. Examples of this kind of device include a flash memory device, a ROM (Read Only Memory), a PROM (Programmable ROM), an EPROM (Electrically Programmable ROM), an EEPROM (Electrically Erasable and Programmable ROM), and a resistive memory (for example, a PRAM (Phase-change RAM), a FRAM (Ferroelectric RAM), and a RRAM (Resistive RAM)).
In order to satisfy performance and price requirements, many consumer products use nonvolatile memory devices. However, these devices have drawbacks. For example, conventional nonvolatile devices have a two-dimensional or plane-type configuration which is limited in terms of storage capacity and, more particularly, the number of memory cells that exist per unit area. To overcome these drawbacks, three-dimensional memory devices have been proposed. However, the initial designs of these devices have proven to be inadequate in a number of respects.